The world’s luckiest human scientists have spent a lot of time around happy dogs and can finally reveal “that happy dogs wag their tails more to the right (from the dog’s point of view), while nervous dogs have a left-dominated swish” and that “fellow canines can spot and respond to these subtle tail differences,” the BBC reports. The former was apparently already known within dogologist (why not?) circles, the latter is new information.

Be warned: the experiment involved animal test-subjects. Scientists “presented dogs with movies of dogs”—Gerard Butler films, right ladies? [clinks white wine]—in which tails wagged to both the right and left. When dogs saw left-wagging tails, “their heart rates picked up and they looked anxious”; right-wagging tails did not produce this effect. When dogs saw 1997 political satire Wag the Dog, they thought it was very clever although de Niro seemed to be phoning it in.

Scientists do not believe that the tail-wagging suggests “that the dogs were intentionally communicating with each other through these movements.” It was more unintentional communication, like how humans’ eyes roll either clockwise or counter-clockwise when they discover that some people just get to play with dogs all day for a living, depending on their levels of jealousy.